全文获取类型
收费全文 | 339667篇 |
免费 | 3046篇 |
国内免费 | 1133篇 |
专业分类
化学 | 150941篇 |
晶体学 | 4178篇 |
力学 | 19631篇 |
综合类 | 7篇 |
数学 | 69306篇 |
物理学 | 99783篇 |
出版年
2021年 | 1451篇 |
2020年 | 1379篇 |
2019年 | 1441篇 |
2018年 | 18499篇 |
2017年 | 19150篇 |
2016年 | 11476篇 |
2015年 | 3887篇 |
2014年 | 3245篇 |
2013年 | 8862篇 |
2012年 | 14093篇 |
2011年 | 28942篇 |
2010年 | 16955篇 |
2009年 | 17445篇 |
2008年 | 23547篇 |
2007年 | 28599篇 |
2006年 | 7987篇 |
2005年 | 15353篇 |
2004年 | 11179篇 |
2003年 | 10491篇 |
2002年 | 7591篇 |
2001年 | 6532篇 |
2000年 | 5222篇 |
1999年 | 3739篇 |
1998年 | 2932篇 |
1997年 | 2841篇 |
1996年 | 2700篇 |
1995年 | 2461篇 |
1994年 | 2317篇 |
1993年 | 2180篇 |
1992年 | 2447篇 |
1991年 | 2435篇 |
1990年 | 2129篇 |
1989年 | 2132篇 |
1988年 | 2176篇 |
1987年 | 2091篇 |
1986年 | 2000篇 |
1985年 | 2933篇 |
1984年 | 2924篇 |
1983年 | 2342篇 |
1982年 | 2542篇 |
1981年 | 2415篇 |
1980年 | 2376篇 |
1979年 | 2339篇 |
1978年 | 2420篇 |
1977年 | 2271篇 |
1976年 | 2225篇 |
1975年 | 2190篇 |
1974年 | 2081篇 |
1973年 | 2212篇 |
1972年 | 1238篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
101.
102.
103.
104.
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices.... 相似文献
105.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
106.
107.
Immobilized Catalysts for Iridium‐Catalyzed Allylic Amination: Rate Enhancement by Immobilization 下载免费PDF全文
Dr. Chandi C. Malakar Prof. Dr. Günter Helmchen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7127-7134
The first immobilized catalyst for Ir‐catalyzed asymmetric allylic aminations is described. The catalyst is a cationic (π‐allyl)Ir complex bound by cation exchange to an anionic silica gel support. Preparation of the catalyst is facile, and the supported catalyst displayed considerably enhanced activity compared with the parent homogeneous catalyst. Up to 43 consecutive amination runs were possible in recycling experiments. 相似文献
108.
109.
Francesca Al Francesca Miraglia Alessandro Orticoni Elda Judica Maria Cotelli Paolo Maria Rossini Fabrizio Vecchio 《Entropy (Basel, Switzerland)》2020,22(11)
Human brain, a dynamic complex system, can be studied with different approaches, including linear and nonlinear ones. One of the nonlinear approaches widely used in electroencephalographic (EEG) analyses is the entropy, the measurement of disorder in a system. The present study investigates brain networks applying approximate entropy (ApEn) measure for assessing the hemispheric EEG differences; reproducibility and stability of ApEn data across separate recording sessions were evaluated. Twenty healthy adult volunteers were submitted to eyes-closed resting EEG recordings, for 80 recordings. Significant differences in the occipital region, with higher values of entropy in the left hemisphere than in the right one, show that the hemispheres become active with different intensities according to the performed function. Besides, the present methodology proved to be reproducible and stable, when carried out on relatively brief EEG epochs but also at a 1-week distance in a group of 36 subjects. Nonlinear approaches represent an interesting probe to study the dynamics of brain networks. ApEn technique might provide more insight into the pathophysiological processes underlying age-related brain disconnection as well as for monitoring the impact of pharmacological and rehabilitation treatments. 相似文献